Fabric



Fatented Apr. 17, 1945 UNITED STATES PATENT orrics p,

FABRIC James Robertson Myles and Donald Whittaker,

Northwich, and Francis Joseph Siddle, Man-' chester, England, assignors to Imperial Chemical Industries Limited, a corporation of Great Britain No Drawing. Application July 28, 1942, Serial No. 452,672. In Great Britain November 8, 1940 1- Claim. (Cl. 117-7) oration of the solvent; films can ,be obtained which shrink during formation and which have a high tensile strength and a low extension under load. The film should also be smooth and light weight, non-inflammable, flexible at low temperatures' and resistant to other conditions of exposure. The solution used must be of sufllcient concentration and suitable viscosity for ready application.

According to the present invention, a fabric is treated .fOr the purpose referred to by appl ing tothe fabric by the customary methods of doping, a solution in a suitable volatile solvent or solvent mixture which contains the material obtained by chlorinating solid polymers of ethylene at a temperature below about 60 C. to a chlorine content of. about (so-70% by weight, and

preferably also one or more substances which inhibit the. liberation of free hydrogen chloride from chlorinated polythenes under the conditions of exposure to light and/or heat, and if desired, other film-forming materials and/or plasticisers. A further feature of the invention comprises the provision of a dope for carrying out the aforesaid process, the said dope-consisting of a solution containing chlorinated solid polythenes having a chlorine content of 60-70% by weight made by chlorination ata temperature below 60 C., and, if desired, other constituents.

In treating fabrics by these dopes, it is essential that the first coat shall penetrate the fabric and thus adhere firmly to it. Subsequent coats may be applied to the surface. Thus we prefer to brush the first coat of dope into the fabric, and subsequent coats may be sprayed, brushed or otherwise applied as convenient. The polymers of ethylene can be halogenated by treatment with one or more halogens in the manner disclosed in U. S. Patent 2,183,556. The chlorinated polymers of ethylene to which this invention relates are made from normally solid polymers of ethylene of mean molecular weight above 2000, preferably above 8000, as measured b the Staudinger solution viscosity method. The chlorination .is carried out by treatment of solid polymers of ethylene in presence of an inert liquid medium at a temperature below about 60 C. with chlorine or substances capable of 55 introducing chlorine. The most suitable inert liquid medium is carbon tetrachloride, but other chlorine-stable liquids may be employed.

Chlorinated polymers of ethylene of low chlo- 5 rine content do not act alone as dopes because they are notsufficiently soluble in the preferred solvents and solvent mixtures, and the extension Chlorinatedv polymers under load is too great. of ethylene prepared at high temperatures do 10 not act alone as dopes because the materials creep under load. Thus when a fabricfiiilndcr tension'is impregnated with either of these materials alone the tautness of the fabric is not improved. I

Mixtures of two or more chlorinated polymers of ethylene such as are described and ,claimed in U. S. Patent 2,268,162 may be employed when their mean chlorine content is high, preferably about -70% by weight, and when the chlo- 20 rinated polymers of ethylene have been prepared at temperatures below 60 C.

v These chlorinated polymers of ethylene have a slight tendency to decompose when exposed for long periods to heat and light, with evolution of 2 hydrogen chloride which may impair the fabric. For this reason we prefer to incorporate in the chlorinated polymers. of ethylene used in the present invention a small amount of one or more dopes generally contain pigments suspended in the solution or dyes dissolved or suspended in the solution which screen the doped fabric from the light and thus prevent the light from causing decomposition of the dope. The same purpose may also be achieved by incorporating such materials as are described and claimed in application No. 373,380, filed January 6, 1941, now U. Sr

Patent 2,316,481. When the fabrics are to be exposed to elevated temperatures, we also prefer to add one or mor substances which inhibitsthe decomposition of c orinated polymers of ethylene at elevated temperatures, such as those described in application 410,592,'flled September 12,

1941, or ethylene oxide derivatives which have a boiling point above C. such. as phenyl glycide ether and p naphthyl glycide ether. It is sometimes desirable also to obtain a doped fabric of increased flexibility and this can .be done by materials which inhibit this deterioration. These as already defined. Such materials include chlorinated rubber, polymethyl methacrylate, polyvinyl derivatives and the like. Thus, in addition to chlorinated polymers of ethylene, the dope may contain pigments, light stabilisers, heat stabilisers, plasticisers, other film-forming materials or any or all of these.

Two coats of the pigmented solution of the chlorinated ethylene polymer were applied by brushing and in each case the amount of halogenated ethylene'polymer applied was 1 oz./sq. yd. The first coat was allowed to dry before I the second coat was applied.

Suitable solvents have a boiling point below 200 C. and a melting point below 0., and we prefer to use aromatic compounds such as benzene, toluene, xylene or chlorinated hydrocarbons, or ketones excluding acetone, or esters such as ethyl and amyl acetates, or mixtures containing them. Acetone and petroleum hydrocarbons,

solvent naphtha and the like, may also be added advantageously as diluents to the solvent.

A convenient solution may contain 540% by weight of chlorinated polymers of ethylene and have a viscosity of 1-6poises, :but these limits are not critical and vary with the particular materials and methods of app fi employed- It is desirable to use as little dope as will effect tautening and this usually amounts to about 1-5 ounces per square yard.

The invention is illustrated but not restricted by the following examples:

Example 1 100 g. of chlorinated ethylene polymer containing 65% by weight of chlorine, made by chlorinating an ethylene polymer of mean molecular weight 14,000 in suspension in carbon tetrachloride at a temperature of -30 C., was milled in a ball mill at room temperature with 10 g. of finely divided ferric oxide, 1 g. phenyl salicylate, 2 g. of lead tartrate and 200 cos. of a mixture of equal volumes of benzene and toluene. To the The tautness of the fabric was measured 24 hours after the application of the second coat, and the depression was found to be only 1.05

The coated fabric was non-inflammable and had a smooth waterproof surface, flexible at low temperatures and capable of being heated to C. for extended periods without material loss of tautness.

. Example 2 100 g. of chlorinated ethylene polymer contain- Example 3 100 g. of chlorinated ethylene polymer containing 62% of chlorine by weight made by ch10- rinating an ethylene polymer of mean molecular resulting thick paste was added gradually 270 ccs. benzene and 270 cos. toluene and 185 cos. of acetone. Between each addition of the liquids, ball milling was continued in order to give a line suspension cf the pigment in the dope.

The resulting dope was a smooth liquid, of iriscosity about-2 poises at 20 0., suitable for application to a properly prepared fabric by brushing or spraying.

A test panel was prepared by stretching standard linen aeroplane fabric on a 1 foot square metal frame, with a tension of 2 lbs. per inch of weight 12,000, while maintaining the temperature below'60 C., was stirred cold with 900 cos. of a mixture of equal volumes of toluene, methylethyl ketone andethyl acetate. The resulting dope was tested on a fabric by the method given in Example 1. The depression of the undoped fabric under the Standard load was 3.2 mms; after doping and drying the depression was reduced to 1.2 mms. After exposing the test panel in the open air for 3 months, the depression was 1.3 mms.

We claim:

An article of manufacture comprising a frame and a tautened flexible fabric attached to and covering said frame, said tautened fabric being impregnated and coated with the dried film of a solution in organic solvent boiling below 200 C., and melting below 10 C. of the chlorinated ethylene polymer resulting from chlorination of solid ethylene polymer at a temperature below 60 C., to a chlorine content of 60% to by weight.

JAMES R. MYLES. DONALD WHITTAKER. FRANCIS JOSEPH SIDDLE. 

